Search

Objective: In order to study the biodiversity of actinomycetes isolated from salt lakes in Hami, Xinjiang, and the characteristics of enzymes thereof., Methods: Soil samples in salt lakes Hami were isolated with 4 isolation media containing 5% and 10% NaCl (w/v) by dilution-plate method. The activities of lipase, galactosidase, amylase, esterase and cellulose from isolated strains were qualitatively detected by using five selective media. Based on morphological characteristics, test of salt tolerance, antibacterial activitity, enzymatic characters and sequencing of 16S rRNA gene, strains were selected for phylogenetic analysis., Results: A total of 63 actinomycetes were isolated from salt lake in Hami, of which 47 strains were halophilic actinomycetes. The antibacterial activity results showed that 23 strains had antibacterial activity toward Bacillus subtilis and other pathogens. Three strains produced proteinase, 46 strains produced amylase, 14 strains produced esterase, 34 strains produced galactosidase, and 5 strains produced cellulase. Analysis of 16S rRNA gene sequence indicated relatively rich genotypic diversity among these actinomycetes., Conclusion: There were abundant actinomycetes resources in the salt lakes in Hami, Xinjiang. The strains had very promising enzyme activities.

Objective: To know halophilic actinomycetes and their enzyme-producing ability from mud volcano in Usu County, Xinjiang, China., Methods: Soil samples in mud volcano were isolated with five isolation media containing 5% and 10% NaCl (w/v) with dilution-plate method. The activities of lipase, galactosidase, amylase, esterase and cellulase from isolated strains were qualitatively detected by using five selective media. Base on morphological characteristics, test of salt tolerance, screening of enzymatic characters and sequencing of 16S rDNA gene, strains were selected for phylogenetic analysis., Results: A total of 43 halophilic actinomycetes and 3 extreme halophilic actinomycetes were obtained. Screening results for enzyme activity showed that 4 halophilic actinomycetes produced lipase, 30 strains produced galactosidase, 27 strains produced amylase, 6 strains produced esterase, 4 strains produced cellulose and 1 strain produced 4 enzymes simultaneously. According to 16S rDNA sequence analysis, 24 of 25 detected sequences were affiliated with Nocardiopsis, and the other one was Streptomyces. In the phylogenetic tree, strain 10006 producing 2 enzymes and Nocardiopsis exhalans (AY03600) showed 96.64% similarity (less than 97%), which indicated that strain 10006 was a possible new species., Conclusion: There are plenty of galactosidase or amylase-producing halophilic actinomycetes and higher enzyme-producing diversity of Nocardiopsis in Usu mud volcano. In addition, there are potential microbial resources in this extreme environment.

Objective: Recently H5N1 subtype avian influenza virus (AIV) is capable of mortality to aquatic bird. The molecular basis for the virulence of this virus is still poorly understood., Methods: We characterized two H5N1 subtype viruses, A/mallard/Huadong/Y/2003 (Y) is nonpathogenic to mallard whereas A/mallard/Huadong/S/2005 (S) is highly pathogenic to mallard. Using reverse genetics, we constructed a series of single-gene or multiple-gene reassortants from these two viruses., Results: Substitution of single-gene for PB2, PB1, PA (3P), HA and of combination for 3P gene resulted in complete attenuation of S virus in mallard. However, these corresponding substitutions only slightly increased virulence of Y virus in mallard. Other gene segments had little contribution to the virulence of both viruses., Conclusion: These results indicate that the pathogenicity of H5N1 AIV to mallard was regulated by multiple gene segments, and these regulations had more sensitive effect on highly pathogenic virus backbone than on low pathogenic virus backbone.

Infection in chicken flocks on a farm, where AI outbreak took place in 1998, was monitored in a four-year consecutive period and 22 H9N2 subtype viruses were isolated. The HA gene and antigenicity of 9 strains among isolates were compared with that of isolate of 1998. The results indicated that mutations of HA genes of H9 subtype influenza A viruses were observed during five years. However these mutations of HA genes didn't lead to sufficient antigenic variation to change the cross-protective pattern of these strains. These findings may be fruitful for making further study of genetic mutations of AIVs in the field and improving the control strategies.

Eight full-length genes of an H9N2 subtype avian influenza virus A/Chicken/Shanghai/F/ 98(H9N2), were amplified by RT-PCR and rapid amplification of cDNA ends (RACE) and sequenced. The results of phylogenetic analysis showed that A/Chicken/Shanghai/F/98 was entirely different from Quail/Hong Kong/G1/97 which was directly related to human infection with avian influenza virus in Hong Kong, whereas its HA, NA, M and NS genes belonged to A/Chicken/Beijing/ 1/94-like sublineage with the nucleotide homology of 96.7%, 96.4%, 97.5% and 98.0% respectively. The homology of NA gene between A/Chicken/Shanghai/F/98 and A/Duck/Hong Kong/Y280/ 97 was 97.4% and they both lost 9 nucleotides between nt 205 to 206. However, the PB2, PB1, PA, NP genes did not show any close relationship with those of the three known sublineages and the later three didn't share immediate ancestors with available isolates whose sequences had been reported. Therefore, A/Chicken/Shanghai/F/98 is a product of natural reassortment between H9N2 avian influenza viruses from different sublineages.